| 摘要 |
PURPOSE:To reduce the collector-substrate coupling capacitance which has the largest percentage of the coupling capacitance of the transistor and also reduce the base and collector capacitance by forming the buried collector directly under the active region of the transistor only. CONSTITUTION:A P<+> type channel-cutting region 7 is formed by implanting boron into a P type semiconductor substrate 1 by ion-implantation and an N<+> type buried layer 3 is formed by injecting As ions after drilling an operture in the region 7. Low density poly-silicon 4 is formed by CVD method and melted by laser and the like. By above process, the poly-silicone on the buried collector layer 3 becomes single crystal silicon and the grain size of the poly-silicon on the oxide film becomes larger. The recess obtained by the neighborhood of this single crystal is oxidized and made grow to the same height as the poly-silicon. Then the oxide film is removwd and a base region 11, an emitter region 12 and a collector region 13 are formed in such a manner that the single crystal part is limited only to the extent in which the depletion layer of the P-N junction directly under the emitter is extended. |
